The shape of the lesson
By the end of the lesson, learners can
- Distance, time, and the ratio between them: Set a constant speed and release the trolley.
- Speed, velocity, and average speed.
- Convert km to m and minutes to s before using v = s ÷ t.
- Average speed = total distance ÷ total time, not the average of the speeds.
- Velocity needs a direction; speed does not.
One picture every idea returns to
Speed is the distance travelled per unit time, a scalar. Velocity is speed in a stated direction, a vector. Both come from v = s / t, measured in metres per second (m/s).
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, How fast, and which way.. Speed tells you how quickly distance is covered. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Distance, time, and the ratio between them | Set a constant speed and release the trolley. Project tab 1 of the lab (Speed and velocity) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Speed, velocity, and average speed | Speed, velocity, and average speed. | Numbered Heads Together |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 15 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Speed, velocity, and average speed, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Numbered Heads Together
Teams of four number off. Put up a question, give the team time to make sure every member can answer, then call a number: that student answers for the team, so nobody can leave the thinking to someone else.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Two cars travelling at the same speed in opposite directions have different velocities, because velocity includes direction. | When a question gives a direction, or asks about a change in direction, it is testing velocity, and the sign or compass bearing is a required part of your answer. |
Speed and velocity: worksheet
6 questions, 15 marks. Written in the style of the papers; no past paper question is reproduced.
Define speed, and state its SI unit.
Explain the difference between speed and velocity, using an example.
A runner covers 240 m in 30 s at a steady rate. Calculate the speed.
A train travels 3.0 km in 10 minutes. Calculate its average speed in m/s.
A walker covers the first 60 m of a path at 3.0 m/s, then the next 60 m at 6.0 m/s. Calculate the average speed for the whole 120 m.
Two cars drive along the same straight road at 25 m/s, but in opposite directions. State whether their speeds are the same and whether their velocities are the same, explaining your answer.
Answer key and marking notes
- Speed is the distance travelled per unit time. ✓
- SI unit: metre per second (m/s). ✓
- Speed is a scalar (magnitude only); velocity is a vector (speed in a stated direction). ✓
- Example: 20 m/s is a speed; 20 m/s due north is a velocity. ✓
- v = s ÷ t = 240 m ÷ 30 s
v = 8.0 m/s
Convert first. 3.0 km = 3000 m; 10 min = 600 s.
v = 3000 m ÷ 600 sv = 5.0 m/s
Time for each part.
t₁ = 60 ÷ 3.0 = 20 s ; t₂ = 60 ÷ 6.0 = 10 sAverage. total distance ÷ total time = 120 m ÷ 30 s
average speed = 4.0 m/s
not 4.5 m/s; you cannot just average 3 and 6
- Their speeds are the same (both 25 m/s), because speed has magnitude only. ✓
- Their velocities are different, because velocity includes direction and they travel in opposite directions. ✓
2 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
A runner completes 400 m in 50 s. What is the average speed?
- A0.125 m/s
- B8.0 m/s
- C80 m/s
- D350 m/s
A car drives 6 km north, then 6 km south, arriving back at its start. The whole trip takes 30 minutes. What is the average velocity for the whole journey?
- A0 km/h
- B12 km/h
- C24 km/h
- D48 km/h
Quiz key
average speed = 400 ÷ 50 = 8.0 m/s. Option A inverts the formula (time ÷ distance); C is a factor-of-ten slip; D subtracts the numbers.
The car returns to its starting point, so the displacement is zero and the average velocity is zero. Option C (24 km/h) is the average speed: total path 12 km in 0.5 h. This is the speed-versus-velocity distinction.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.